Method for discriminating organic agricultural products from conventional agricultural products by using nitrogen isotope index

ABSTRACT

The present invention provides a method for discriminating an organic farmland from a conventional farmland, comprising; (a) measuring an amount of nitrogen isotope in a soil sample of a farmland; (b) calculating a nitrogen isotope index according to the formula (1) using the resultant nitrogen isotope value and (c) determining whether the farmland belongs to an organic farmland or a conventional farmland. According to the present invention, it is possible to objectively discriminate an organic farmland from a conventional farmland or discriminate an organic crop from a conventional crop.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for discriminating an organiccrop from a conventional crop, or an organic farmland from aconventional farmland by using a nitrogen isotope index in a soil sampleor crop sample.

2. Description of the Related Art

In conventional cultivation practice, an excess amount of chemicalfertilizer and pesticides have been used to increase the productionyield. However, those chemical fertilizer and pesticides have causedecological disturbance such as accumulation of salts and imbalance ofnutrients in soil, decrease in the number of soil microorganisms andnatural predators; water contamination; and safety problems inagricultural products, etc. With respect to these problems, it isanticipated that international trade volume in organic crop will beincreased by way of international efforts to link agriculture,environment and trade, and thus to make international regulations toresolve the above problems. Further, a standard for an organic crop willbe set up in Codex. OECD is planning to evaluate agricultural policiesof each country by developing environmental index of agriculture in 13divisions.

In response to these international efforts, “Law for promotingenvironmentally favorable agriculture” and “enforcement Law thereof”have been made in Korea to promote agriculture in an environmentallyfavorable way and to promote the production of value-added agriculturalproducts by introducing a quality certification system therefor.According to the standard adopted in the quality certification systemfor environmentally favorable agricultural products, i.e., QualityStandard for crop (Korea), agricultural products are classified intofour categories: low-pesticide agricultural products (the amount of usedsynthesized pesticide is ½ or lower of the standard amount thereof andthe amount of used chemical fertilizer is ½ or lower of the recommendedamount thereof); pesticide free agricultural products (no use ofsynthesized pesticides and the amount of used chemical fertilizer is{fraction (1/3)} or lower of the recommended amount thereof);transitional organic agricultural products (no use of synthesizedpesticides more than 1 year and no use of chemical fertilizer); andorganic agricultural products (no use of synthesized pesticides morethan 3 years and no use of chemical fertilizer). Thus, it is critical todetermine whether a synthesized pesticide or a chemical fertilizer hasbeen used or not in evaluating agricultural products according to thequality certification system.

Synthesized pesticides can be investigated by monitoring residualpesticides in a crop or soil sample. On the contrary, chemicalfertilizer can be investigated only by an indirect method such as dataon farming and an analysis of chemical properties of corresponding soil.However, there were problems that data on farming may be arbitrarilymade by a farmer, and although the chemical properties of soil aredirectly affected by the application rates of fertilizers thereto, thereis no scientific relationship between the chemical properties of soiland a type of fertilizer (chemical fertilizer or organic fertilizer)applied thereto. According to the state of the art, it is impossible toobjectively determine whether a chemical fertilizer or an organicfertilizer has been used in a soil. Thus, there is a need for a methodfor determining whether chemical fertilizer or organic fertilizer hasbeen used in soil of interest. Such a method is also needed to satisfythe consumer's need to know whether an agricultural product of interestwas grown with chemical fertilizer or organic fertilizer.

There has been an attempt to determine the source of water contaminationon the basis that a nitrogen isotope ratio of chemical fertilizer isdifferent from that of livestock manure (Kohl et al, 1971, Fertilizernitrogen: contribution to nitrate in surface water in a corn beltwatershed, Science 174: 1331-1334). An analysis for the nitrogen isotopewas employed for the purpose of studying the source of watercontamination (lqbal et al, 1997, Nitrogen isotope indicators ofseasonal source variability to groundwater, Environmental Geology 32:210-218). However, the analysis for nitrogen isotope has never been usedto investigate the kind of fertilizer (chemical vs. organic) applied toa farmland or to discriminate a crop grown with organic fertilizer froma crop grown with a chemical fertilizer.

The inventors have statistically analyzed distribution of nitrogenisotope in chemical fertilizer and organic fertilizer, and carried outexperiments to examine the effect of chemical fertilizer or organicfertilizer on the nitrogen isotope index of a soil and a crop therefrom,and completed the present invention.

SUMMARY OF THE INVENTION

The present invention provides a method for discriminating an organicfarmland from a conventional farmland.

The present invention provides a method for discriminating an organiccrop from a conventional crop.

The present invention provides a method for discriminating an organiccrop from a conventional crop or an organic farmland from a conventionalfarmland.

In one aspect, the present invention provides a method fordiscriminating an organic farmland from a conventional farmland,comprising;

-   -   (a) measuring an amount of nitrogen isotope in a soil sample of        a farmland;    -   (b) calculating a nitrogen isotope index according to the        formula (I) using the obtained nitrogen isotope value:        δ¹⁵ N=[R sample/R reference−1]×1,000   (I)        wherein δ¹⁵N is a nitrogen isotope index, R sample and R        reference are ¹⁵N/(¹⁵N+¹⁴N) ratio of sample and reference,        respectively; and    -   (c) determining whether a farmland belongs to a organic farmland        or a conventional farmland.

In one aspect, the present invention also provides a method fordiscriminating an organic crop from a conventional crop, comprising;

-   -   (a) measuring an amount of nitrogen isotope in a crop sample;    -   (b) calculating a nitrogen isotope index according to the        formula (I) using the obtained nitrogen isotope value:        δ¹⁵ N=[R sample/R reference−1]×1,000   (I)        wherein δ¹⁵N is a nitrogen isotope index, R sample and R        reference are ¹⁵N/(¹⁵N+¹⁴N) ratio of sample and reference,        respectively; and    -   (c) determining whether a crop belongs to a organic crop or a        conventional crop.

The terms, as used herein, are referred to as follows otherwisementioned. The term “nitrogen isotope” refers to nitrogen isotopesincluding ¹⁵N and ¹⁴N. The term “nitrogen isotope ratio” refers to aratio of heavy nitrogen (¹⁵N) to total nitrogen (¹⁵N+¹⁴N), i.e.,represented by ¹⁵N/(¹⁵N+¹⁴N). Further, the term “nitrogen isotopeindex(δ¹⁵N)(%)” of a sample refers to a normalized index of a nitrogenisotope ratio of a sample to that of a reference sample defined asfollowing formula (I):δ¹⁵ N=[R sample/R reference−1]×1,000   (I)wherein δ¹⁵N is a nitrogen isotope index, R sample and R reference are15N/(¹⁵N+¹⁴N) ratio of sample and reference, respectively.

Atmospheric nitrogen (N₂) is typically used as reference material. Inthis case, the δ¹⁵N value for atmospheric nitrogen is 0% by definition.The higher level of nitrogen isotope index means higher level of ¹⁵N ina sample. Typically, a nitrogen isotope index of an organic fertilizeris higher than that of a chemical fertilizer. FIG. 1 illustrates averageof the nitrogen isotope index for 8 types of chemical fertilizers and 27types of organic fertilizers, which are commercially available in Korea.As shown in FIG. 1, the average nitrogen isotope index for organicfertilizers (16.7±2.3%) is higher than that of chemical fertilizers(−1.5±1.50%). The present invention is made based on such differences inthe nitrogen isotope index between chemical fertilizer and organicfertilizer.

Moreover, the term “organic farmland”, as used herein, generally refersto a farmland to which an organic fertilizer has been applied for acertain period. An organic farmland includes a farmland to which anorganic fertilizer has been applied as a sole fertilizer source or as asubstantially major fertilizer for a certain period. The term “organiccrop” generally refers to a crop that harvested after having been grownby using organic fertilizer and includes an organic crop andtransitional organic crop under Quality Standard for crop (Korea).However, the terms “organic farmland” and “organic crop” are notintended to be limited to the above mentioned meaning since the exactmeanings of “organic farmland” and “organic crop” can be defined byassigning a specific nitrogen isotope index values at a specificapplication of the present invention.

The term “organic fertilizer” refers to a fertilizer produced byprocessing a biological materials such as animal manures and plantsmaterials, and includes both an organic fertilizer and byproductsfertilizer under Official Standard for fertilizers (Korea). Urea can beclassified as an organic fertilizer if it is derived from an organism,while it can not be classified as an organic fertilizer if it isproduced by a synthesis through a chemical engineering process.

The term “conventional cultivation” refers to a type of cultivationusing a chemical fertilizer, which is a typical type of cultivation. Theterm “conventional farmland”, as used herein, generally refers to a typeof farmland to which chemical fertilizer has been applied as a solefertilizer source or as a substantially major fertilizer for a certainperiod. The term “conventional crop” generally refers to a crop thatharvested after having been grown by using a chemical fertilizer.However, the terms “conventional farmland” and “conventional crop” arenot intended to be limited to the above mentioned meaning since theexact meanings of “conventional farmland” and “conventional crop” can bedefined by assigning a specific nitrogen isotope index values at aspecific application of the present invention.

In step (a) of the present method, the measurement of the amount of anitrogen isotope may be achieved by using a conventional apparatus whichis used in the art, such as a stable isotope ratio mass spectrometer.The soil sample for the measurement of the nitrogen isotope amount maybe prepared from the whole soil or by selecting a portion thereof havinga specific range of particle size. Further, the amount of nitrogenisotope of the soil sample may be measured for whole nitrogen includingammonium(NH₄ ⁺) nitrogen, nitrate(NO₃ ⁻) nitrogen and organic nitrogen,as well as for the foregoing each component.

The present invention may be applied to the crops, for examples, but notlimited to, a leaf vegetables such as a Chinese cabbage, greens forpickling, a Brassica campestris (a Chinese spinach-like greenvegetable), a cabbage, a cauliflower, a broccoli, a Brussels sprout, anonion, a Welsh onion, a garlic, a scallion, a leek, an asparagus, alettuce, a green for salad (which is called Saladana in Japan), acelery, a spinach, a crown daisy, a parsley, a trefoil (which is calledMitsuba in Japan and is useful as herb), a dropwort, an udo (which is anAralia cordata), a Japanese ginger, a Japanese butterbur and a labiate;a fruit vegetables such as a cucumber, a pumpkins, a water melon, amelon, a tomato, an eggplant, a pimento, a strawberry, a kidney bean, abroad bean, a pea, a soybean and a corn; and a root vegetables such as aradish, a turnip, a burdock, a carrot, a potato, a taro, a sweet potato,a ginger, and a lotus. Other crops to which the present invention can beapplied, include a rice, a barley, a wheat and other flowery plants, butnot limited to these examples. Preferably, the crops are a leafvegetables such as a Chinese cabbage, greens for pickling, a Brassicacampestris (a Chinese spinach-like green vegetable), a cabbage, acauliflower, a broccoli, a Brussels sprout, an onion, a Welsh onion, agarlic, a scallion, a leek, an asparagus, a lettuce, a green for salad(which is called Saladana in Japan), a celery, a spinach, a crown daisy,a parsley, a trefoil (which is called Mitsuba in Japan and is useful asherb), a dropwort, an udo (which is an Aralia cordata), a Japaneseginger, a Japanese butterbur and a labiate. In step (c) of the presentmethod, determination whether a farmland belongs to an organic farmlandor a conventional farmland, or determination whether a crop belongs toan organic crop or a conventional crop can be achieved by comparing theobtained nitrogen isotope index in a sample of a farmland or a crop withthat of reference farmland or crop sample.

In one embodiment of the present invention, the present inventionprovides a method for discriminating an organic farmland from aconventional farmland by using a nitrogen isotope index, comprising;

-   -   (a) measuring an amount of a nitrogen isotope of whole nitrogen        in a soil sample from a farmland;    -   (b) calculating a nitrogen isotope index according to the        formula (I) using the obtained nitrogen isotope value:        δ¹⁵ N=[R sample/R reference−1]×1,000   (I)        wherein δ¹⁵N is a nitrogen isotope index, R sample and R        reference are ¹⁵N/(¹⁵N+¹⁴N) ratio of sample and reference,        respectively; and    -   (c) determining whether a farmland belongs to an organic        farmland or a conventional farmland.

In step (c), it is preferable that if the nitrogen isotope index is 5%or lower, the farmland is determined to be a conventional farmland, andif the nitrogen isotope index is 8% or higher, the farmland isdetermined to be an organic farmland. This criteria is based on a factthat the nitrogen isotope index for a conventional farmland to whichchemical fertilizer had been applied was about 5.9±0.7%, and an organicfarmland to which an organic fertilizer had been applied was 8.8±0.9%(see FIG. 2). However, it is not intended to limit the scope of thepresent invention to this specific criteria, since the nitrogen isotopeindex may be dependent on the type of soil, type of organic fertilizerand the duration of organic cultivation, etc. In another embodiment ofthe present invention, the present invention provides a method fordiscriminating an organic farmland from a conventional farmland by usinga nitrogen isotope index, comprising;

-   -   (a) measuring an amount of a nitrogen isotope of nitrate (NO₃ ⁻)        in a soil sample of a farmland;    -   (b) calculating a nitrogen isotope index according to the        formula (I) using the obtained nitrogen isotope value:        δ¹⁵ N=[R sample/R reference−1]×1,000   (I)        wherein δ¹⁵N is a nitrogen isotope index, R sample and R        reference are ¹⁵N/(¹⁵N+¹⁴N) ratio of sample and reference,        respectively; and    -   (c) determining whether a farmland belongs to an organic        farmland or a conventional farmland.

In step (c), it is preferable that if the nitrogen isotope index is 4%or lower, the farmland is determined to be a conventional farmland, andif the nitrogen isotope index is 7% or higher, the farmland isdetermined to be an organic farmland. These criteria are based on a factthat the nitrogen isotope index for a conventionally cultivated farmlandto which a chemical fertilizer had been applied was about 4.7±1.1%, andan organic farmland to which an organic fertilizer had been applied was11.6±4.5% (see FIG. 3). However, it is not intended to limit the scopeof the present invention to this specific criteria, since the nitrogenisotope index may be dependent on the type of soil, type of organicfertilizer and the duration of organic cultivation, etc.

In yet another embodiment of the present invention, the presentinvention provides a method for discriminating an organic crop from aconventional crop by using a nitrogen isotope index, comprising;

-   -   (a) measuring an amount of a nitrogen isotope of whole nitrogen        in a crop sample harvested from a farmland;    -   (b) calculating a nitrogen isotope index according to the        formula (I) using the obtained nitrogen isotope index:        δ¹⁵ N=[R sample/R reference−1]×1,000   (I)        wherein δ¹⁵N is a nitrogen isotope index, R sample and R        reference are ¹⁵N/(¹⁵N+¹⁴N) ratio of sample and reference,        respectively; and    -   (c) determining whether a crop belongs to an organic crop or a        conventional crop.

In step (c), it is preferable that if the nitrogen isotope index is 3%or lower, the crop is determined to be a conventional crop, and if thenitrogen isotope index is 8% or higher, the crop is determined to be anorganic crop (see FIG. 4 and FIG. 5). A preferable crop includes, butnot limited to, a leaf vegetables such as a Chinese cabbage, greens forpickling, a Brassica campestris (a Chinese spinach-like greenvegetable), a cabbage, a cauliflower, a broccoli, a Brussels sprout, anonion, a Welsh onion, a garlic, a scallion, a leek, an asparagus, alettuce, a green for salad (which is called Saladana in Japan), acelery, a spinach, a crown daisy, a parsley, a trefoil (which is calledMitsuba in Japan and is useful as herb), a dropwort, an udo (which is anAralia cordata), a Japanese ginger, a Japanese butterbur and a labiate.However, it is not intended to limit the scope of the present inventionto this specific criteria, since the range of the nitrogen isotope indexmay be dependent on the type of soil, a type of an organic fertilizerand the duration of organic cultivation, etc.

Moreover, in another embodiment of the present invention, the presentinvention provides a method for discriminating an organic crop from aconventional crop, comprising;

-   -   (a) measuring an amount of nitrogen isotope in a crop sample        during the cultivation period at appropriate intervals;    -   (b) calculating a pattern of nitrogen isotope index according to        the formula (I) using each of the obtained nitrogen isotope        value:        δ¹⁵ N=[R sample/R reference−1]×1,000   (I)        wherein δ¹⁵N is a nitrogen isotope index, R sample and R        reference are ¹⁵N/(¹⁵N+¹⁴N) ratio of sample and reference,        respectively; and    -   (c) determining whether a crop belongs to a organic crop or a        conventional crop:

In step (a) of the present method, the amount of nitrogen isotope for acrop is a measured during cultivation period of the crop at appropriateintervals. In this way, a nitrogen isotope fluctuation patterns can beobtained by measuring the amount of nitrogen isotope.

In step (c) of the present method, it is preferable that if the nitrogenisotope index exhibits an increasing trend during cultivation period,the crop is determined to be a conventional crop during the cultivationof which a chemical fertilizer was used as a sole fertilizer source inthe early growth period; if the nitrogen isotope index exhibits adecreasing trend after initial increasing trend during the cultivation,the crop is determined to be a conventional crop during the cultivationof which a chemical fertilizer was used separately as a basal fertilizerin the early growth period and as an additional fertilizer in the lattergrowth period; if the nitrogen isotope index exhibits almost nofluctuations or a slight decreasing trend during cultivation period, thecrop is determined to be an organic crop during the cultivation of whichan organic fertilizer was used as a sole fertilizer; and if the nitrogenisotope index exhibits a decreasing trend after initial no fluctuationduring cultivation period, the crop is determined to be a conventionalcrop during the cultivation of which an organic fertilizer was used as abasal fertilizer in the early growth period and a chemical fertilizerwas used as an additional fertilizer. These criteria are based on aresult of experiment on the fluctuation pattern of nitrogen index of acrop grown with a chemical or organic fertilizer during cultivation (seeFIG. 6). However, it is not intended to limit the scope of the presentinvention to this specific criteria, since the range of the nitrogenisotope index may be dependent on the type of soil, a type of an organicfertilizer and the duration of organic cultivation, etc.

In another embodiment, the present invention provides a method fordiscriminating an organic crop from a conventional crop or an organicfarmland from a conventional farmland, comprising;

-   -   (a) measuring an amount of nitrogen isotope in a soil sample of        a farmland and a crop sample harvested therefrom;    -   (b) calculating a nitrogen isotope index according to the        formula (I) using each of the nitrogen isotope value:        δ¹⁵ N=[R sample/R reference−1]×1,000   (I)        wherein δ¹⁵N is a nitrogen isotope index, R sample and R        reference are ¹⁵N/(¹⁵N+¹⁴N) ratio of sample and reference,        respectively; and    -   (c) comparing the resultant nitrogen isotope index values of the        soil with those of the crop to determine whether the farmland        belongs to an organic farmland or a conventional farmland, or to        determine whether the crop from the farmland belongs to an        organic crop or a conventional crop.

In step (a) of the invention, the nitrogen isotope amount of the soilsample or a crop sample may be measured for a portion of the wholenitrogen including ammonium(NH₄ ⁺) nitrogen, nitrate(NO₃ ⁻) nitrogen andan organic nitrogen, as well as the whole nitrogen.

In step (c) of the present method, it is preferable that if the nitrogenisotope index value of the crop is lower than the nitrogen isotope indexvalue of the soil, the crop is determined to be a conventional crop orthe farmland is determined to be a conventional farmland; if thenitrogen isotope index value of the crop is higher than the nitrogenisotope index value of the soil, the crop is determined to be an organiccrop or the farmland is determined to be an organic farmland. Thesecriteria are based on a result of an experiment on a relationshipbetween the nitrogen isotope index of a soil sample and that of a cropsample therefrom (see FIG. 7). However, it is not intended to limit thescope of the present invention to this specific criteria, since therange of the nitrogen isotope index may be dependent on the type ofsoil, a type of an organic fertilizer and the duration of organiccultivation, etc.

The above-mentioned embodiment of the present invention can be used incombination to provide a more reliable method for discriminating anorganic farmland from a conventional farmland or an organic crop from aconventional crop. For example, the method for discriminating an organicfarmland from a conventional farmland and the method for discriminatingan organic crop from a conventional crop, wherein the crop is harvestedfrom the farmland, can be used in combination. Thus, reliability of boththe methods can be secured since if the farmland where a crop has beengrown has been determined to be an organic farmland, the crop harvestedtherefrom would be most likely an organic crop; On the contrary, if thecrop has been determined to be an organic crop, the farmland where thecrop harvested therefrom would be most likely an organic farmland,thereby increasing a reliability of the method. The present inventionincludes any kind of combinations to increase the reliability of themethod.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 illustrates average nitrogen isotope index values for 8 types ofchemical fertilizers and 27 types of organic compost fertilizers whichare commercially available in Korea;

FIG. 2 illustrates nitrogen isotope index values for a soil sample froma conventional farmland and an organic farmland;

FIG. 3 illustrates nitrogen isotope index values of nitrate for aconventional farmland and an organic farmland;

FIG. 4 illustrates nitrogen isotope index values of whole nitrogen in aChinese cabbage sample which has been grown with an organic compost or achemical fertilizer, respectively;

FIG. 5 illustrates nitrogen isotope index values of crop samples (aChinese cabbage, a lettuce, a spinach, a sesame, a cucumber, a eggplant,a red pepper, a cabbage, a Perilla japonica) which have been grown in aorganic farmland or conventional farmland, respectively;

FIG. 6 illustrates a fluctuation in nitrogen isotope index value of acrop (a maize plant) during the cultivation period with time; and

FIG. 7 illustrates a comparison of nitrogen isotope index values for anorganic farmland and a conventional farmland with those of crops (aChinese cabbage, a lettuce, a spinach, a sesame, a cucumber, a eggplant,a red pepper, a cabbage, a Perilla japonica) grown and harvestedtherefrom.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described in greater detail with referenceto the following examples. The following examples are for illustrativepurposes and are not intended to limit the scope of the invention.

EXAMPLE 1

In this example, a nitrogen isotope amount has been measured and anitrogen isotope index has been determined for 8 types of chemicalfertilizers and 27 types of organic fertilizers which are commerciallyavailable in Korea.

The chemical fertilizers were urea, ammonium sulfate and 6 compoundfertilizers, and the organic fertilizers were an organic fertilizer orbyproducts fertilizer under Official Standard for fertilizers (Korea)including composted pig manure, composted chicken manure, and compostedcow manure. The nitrogen isotope content and index were measured anddetermined by using a continous-flow stable isotope ratio massspectrometer (IsoPrime-EA, Micromass, England) linked with a CN-analyzer(Limaux et al., 1999; Monaghan and Barraclough, 1995). The accuracy andreproducibility of the analysis method, which were checked with areference material (RM 8548: IAEA-N2) obtained from International AtomicEnergy Agency (IAEA), were better than 0.4% and 0.2%, respectively.

FIG. 1 illustrates average nitrogen isotope index values for 8 types ofchemical fertilizers and 27 types of organic compost fertilizers whichare commercially available in Korea. As shown in FIG. 1, the averagenitrogen isotope index values for chemical fertilizers and organicfertilizers were −1.54±1.50% and 16.69±2.32%, respectively. Thus, theaverage nitrogen isotope index values for the organic fertilizer washigher than those of the chemical fertilizer. The inventors haveinvestigated whether these differences between the nitrogen isotopeindex values of the organic fertilizer and those of the chemicalfertilizer can be applied to a soil and a crop, and successfullydiscriminated an organic crop from a conventional crop, or an organicfarmland from a conventional farmland based on the nitrogen isotopeindex.

EXAMPLE 2

In this Example, a nitrogen isotope amount and index of whole nitrogenin a soil sample obtained from a conventional farmland to which achemical fertilizer had been applied and an organic farmland to which anorganic fertilizer had been applied, were measured and determined.

Urea and other chemical fertilizers had been applied to the conventionalfarmland for the last 20 years at rates of 200-400 kgNha⁻¹Yr⁻¹. Acomposted pig manure and other various organic fertilizers had beenapplied to the organic farmland for the last 5 years at rates of 300-600kgNha⁻¹Yr⁻¹.

The soil sample was prepared from the surface layer (a soil layer whichis located within in the depth of 0-15 cm from the surface). Thenitrogen isotope index of whole soil nitrogen was measured anddetermined by using a continous-flow stable isotope ratio massspectrometer (IsoPrime-EA, Micromass, England) linked with a CN-analyzer(Limaux et al., 1999; Monaghan and Barraclough, 1995). The accuracy andreproducibility of the analysis method, which were checked with areference material (RM 8548: IAEA-N2) obtained from International AtomicEnergy Agency (IAEA), were better than 0.4% and 0.2%, respectively.

FIG. 2 illustrates nitrogen isotope index values of whole nitrogen for aconventional farmland and an organic farmland. As shown in FIG. 2, thenitrogen isotope index values for the conventional farmland and anorganic farmland were 5.9±0.7% and 8.8±0.9%, respectively. Thus, theexperimentation results indicate that the nitrogen isotope index for asoil was increased by using an organic fertilizer having a highernitrogen isotope index. Therefore, it was possible to discriminate anorganic farmland from a conventional farmland. That is, if a nitrogenisotope index value in a soil sample is lower than 5%, it may bedetermined to be a soil from a conventional farmland, and if a nitrogenisotope index value in a soil sample is 8% or higher, it may bedetermined to be a soil from a farmland.

EXAMPLE 3

In this Example, a nitrogen isotope amount and index of nitrate (NO₃ ⁻)in a soil sample obtained from a conventional farmland to which achemical fertilizer had been applied and an organic farmland to which anorganic fertilizer had been applied, were measured and determined. Themeasurement and determination were carried out in the same way as in theExample 2 except that the types of nitrogen analysed was nitratenitrogen.

FIG. 3 illustrates nitrogen isotope index values of nitrate for aconventional farmland and an organic farmland. As shown in FIG. 3, thenitrogen isotope index values for the conventional farmland and anorganic farmland were 4.7±4.5% and 11.6±4.5%, respectively. Thus, theresults of this experiment indicate that the nitrogen isotope index ofnitrate nitrogen in a soil was increased by using an organic fertilizerhaving a higher nitrogen isotope index. Therefore, it was possible todiscriminate an organic farmland from a conventional farmland. That is,if a nitrogen isotope index value in a soil sample is 4% or lower, itmay be determined to be a soil from a conventional farmland, and if anitrogen isotope index value in a soil sample is 7% or higher, it may bedetermined to be a soil from the farmland.

EXAMPLE 4

In this Example, a nitrogen isotope index of a crop sample which hadbeen grown with an organic fertilizer or a chemical fertilizer wasmeasured. A nitrogen isotope index of a crop sample which had been grownin an organic farmland and a conventional farmland was also measured.

(1) Measurement of Nitrogen Isotope Index of a Crop Sample which hadbeen Grown with an Organic Fertilizer or a Chemical Fertilizer

To discriminate an organic crop from a conventionally cultivated crop byusing a nitrogen isotope index of whole nitrogen, a crop had been grownin an identical soil environment with an organic fertilizer or achemical fertilizer and then a nitrogen isotope index of whole nitrogenfor the crop was measured.

The crop, a Chinese cabbage grown in the soil prepared from aconventional farmland was applied with about 500 kgNha⁻¹ of eachfertilizer, and grown for about 70 days. The Chinese cabbage washarvested and the nitrogen isotope index was measured. To prepare asample, a whole part of the harvested Chinese cabbage was dried at 60°C. and ground to a fine powder. The same apparatus for the analysis of anitrogen isotope ratio as in Example 2 was used. As a control, a Chinesecabbage was grown and harvested without applying neither a chemical noran organic fertilizer. An organic fertilizer A, B, and C were producedfrom Yongin Stock-Raiser's association, Kunwi Stock-Raiser'sassociation, and Sambi Corporation by using various raw materials and acomposting process, and urea produced by chemical synthesis was used asa chemical fertilizer.

FIG. 4 illustrates a nitrogen isotope index value of whole nitrogen in aChinese cabbage sample which has been grown with an organic compost or achemical fertilizer, respectively. As shown in FIG. 4, a nitrogenisotope index of a Chinese cabbage sample grown with organic fertilizerA, B, and C were 17.8±1.57%, 21.2±0.6% and 20.8±1.1%, respectively, anda nitrogen isotope index of the control was 11.3±1.2%, and a nitrogenisotope index of the Chinese cabbage sample grown with a chemicallysynthesized urea was 3.0±1.1%.

(2) Measurement of a Nitrogen Isotope Index of a Crop Sample Grown in anOrganic Farmland or a Conventional Farmland.

A nitrogen isotope index of a crop which had been grown in an organicfarmland or a conventional farmland was measured in the same way as inthe Example 4 (1). The types of crops used in this Example were aChinese cabbage, a lettuce, a spinach, a sesame, a cucumber, aneggplant, a red pepper, a cabbage and a Perilla japonica, and were grownin the range of 30-60 days in accordance with a crop. The organicfarmland was a farmland which had been cultivated at least 5 years withvarious organic fertilizers at rates of 300-600 kgNha⁻¹Yr⁻¹, and theconventional farmland was a farmland which had been cultivated at least20 years with chemical fertilizers (mainly urea) at rates of 200-400kgNha⁻¹Yr⁻¹.

FIG. 5 illustrates nitrogen isotope index value for crop samples (aChinese cabbage, a lettuce, a spinach, a sesame, a cucumber, aneggplant, a red pepper, a cabbage, a Perilla japonica) which had beengrown in an organic farmland or conventional farmland, respectively. Asshown in FIG. 5, a nitrogen iosotope index for a crop which had beengrown in an organic farmland and a conventional farmland were 4.1±1.7%and 14.6±3.3%, respectively.

In accordance with the Example 4 (1) and (2), it was possible todiscriminate an organic crop from a conventional crop by measuring anitrogen isotope index of a crop sample. That is, if a nitrogen isotopeindex value of a crop sample is 3% or lower, it may be determined to bea crop grown in a conventional farmland or with a chemical fertilizer,and if a nitrogen isotope index value for a crop sample is 8% or higher,it may be determined to be a crop grown in an organic farmland or withan organic fertilizer.

EXAMPLE 5

A nitrogen isotope ratio of a crop sample was measured duringcultivation period. To this end, the crop was grown with a chemicalfertilizer (urea) or an organic fertilizer (composted manure) and asample was taken for the measurement at appropriate intervals during thecultivation period.

The crop used in this Example was a maize plant, grown with fertilizerat a rate of 150 kgNha⁻¹ (In case of split application, basal andadditional fertilizer were applied at equal rate; 75 kgNha⁻¹ for each),and the nitrogen isotope ratio of the whole nitrogen was measured for acrop sample at the 30^(th), 40^(th) and 60^(th) day after sowing. Themeasurement was carried out in the same way as in the Example 4(1).

FIG. 6 illustrates a nitrogen isotope index value of whole nitrogen fora crop (a maize plant) during the cultivation period at appropriateintervals. As shown in FIG. 6, the nitrogen isotope index value for thecontrol remained almost the same, and for the crop grown with only ureaas a basal fertilizer, the nitrogen isotope index value for the cropcontinuously increased from 1.1±0.6% at the day 30^(th) to 4.9±0.4% atthe day 60^(th).

On the other hand, for a crop grown with only compost as a basalfertilizer, the nitrogen isotope index decreased slightly from 7.7±0.2%at the day 30^(th) to 7.0±0.2% at the day 60^(th). For a crop grown withurea plus compost as a basal fertilizer, the nitrogen isotope indexvalue increased from 4.5±0.6% at the day 30^(th) to 6.1±0.2% at the day60^(th). On the other hand, for a crop grown with a urea as a basal andan additional fertilizer, the nitrogen isotope index value increasedfrom 1.2±0.6% at the day 30^(th) to 3.6±0.4% at the day 40^(th), andthen decreased to 2.1±0.4% at the 60^(th) day. For a crop grown withcompost as a basal and urea as an additional fertilizer, the nitrogenisotope index value remained substantially the same at the 30^(th)(7.8±0.2%) and 40^(th) day (7.5±0.3%), and then decreased to 5.2±0.2% atthe 60^(th) day by applying an additional fertilizer (at 40^(th) day ofgrowth).

According to this Example, it is possible to determine that if thenitrogen isotope index exhibits an increasing trend during cultivationperiod with time, the crop is determined to be a conventional cropduring the cultivation period of which a chemical fertilizer had beenused as a sole fertilizer in the early growth period; if the nitrogenisotope index exhibits a decreasing trend after initial increasing trendduring cultivation period with time, the crop is determined to be aconventional crop during the cultivation period of which a chemicalfertilizer had been used as a basal fertilizer in the early growthperiod and as an additional fertilizer in the latter growth period; ifthe nitrogen isotope index exhibits almost no fluctuation or a slightdecreasing trend during the cultivation period with time, the crop isdetermined to be an organic crop during the cultivation period of whichan organic fertilizer was used as a sole fertilizer; and if the nitrogenisotope index exhibits a decreasing trend after initial insignificantfluctuating trend during the cultivation period with time, the crop isdetermined to be a conventional crop during the cultivation period ofwhich an organic fertilizer was used as a basal fertilizer and achemical fertilizer was used as an additional fertilizer.

EXAMPLE 6

In this Example, nitrogen isotope index values of a soil sample from afarmland and a crop harvested therefrom was measured and analysed.

The kind of crop, a cultivation period, use and amount of a fertilizerwere the same way as in the Example 4(2) and method for measuring anitrogen isotope was carried out in the same as in the Example 2 and4(2) since the data used in this Example was those of Example 2 for thesoil and those of Example 4(2) for the crop. FIG. 7 illustrates acomparison of nitrogen isotope index values for an organic farmland anda conventional farmland with those of crop (a Chinese cabbage, alettuce, a spinach, a sesame, a cucumber, a eggplant, a red pepper, acabbage, a Perilla japonica) grown and harvested therefrom. As shown inFIG. 7, where a crop had been grown in a conventional farmland, anitrogen isotope index of whole nitrogen in a crop sample harvestedtherefrom was lower than those of the soil of the conventional farmland,while where a crop was grown in an organic farmland, a nitrogen isotopeindex of whole nitrogen in a crop sample harvested therefrom was higherthan those of the soil of the conventional farmland.

According to the results of this Example, it was found that if thenitrogen isotope index of the crop is lower than the nitrogen isotopeindex of the soil of the conventional farmland, the crop may bedetermined to be a conventional crop or the farmland may be determinedto be a conventional farmland; and if the nitrogen isotope index of thecrop is higher than the nitrogen isotope index of the soil of theconventional farmland, the crop may be determined to be an organic cropor the farmland may be determined to be an organic farmland.

According to the present invention, it is possible to discriminate anorganic farmland from a conventional farmland by using a nitrogenisotope index of a soil sample.

According to the present invention, it is also possible to discriminatean organic crop from a conventional crop by using a nitrogen isotopeindex of a crop sample.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A method for discriminating an organic farmland from a conventionalfarmland, comprising: (a) measuring an amount of nitrogen isotope of asoil sample for a farmland; (b) calculating a nitrogen isotope indexaccording to the formula (I) using the obtained nitrogen isotope value:δ¹⁵ N=[R sample/R reference−1]×1,000   (I) wherein δ¹⁵N is a nitrogenisotope index, R sample and reference are ¹⁵N/(¹⁵N+¹⁴N) ratio of sampleand reference, respectively; and (c) determining whether the farmlandbelongs to an organic farmland or a conventional farmland.
 2. The methodaccording to claim 1, if the nitrogen isotope index is 5% or lower, thefarmland is determined to be a conventional farmland, and if thenitrogen isotope index is 8% or higher, the farmland is determined to bean organic farmland.
 3. The method according to claim 1, wherein thenitrogen is nitrate form nitrogen among various nitrogen pools of thesoil sample.
 4. The method according to claim 3, if the nitrogen isotopeindex is 4% or lower, the farmland is determined to be a conventionalfarmland, and if the nitrogen isotope index is 7% or higher, thefarmland is determined to be an organic farmland.
 5. A method fordiscriminating an organic crop from a conventional crop, comprising: (a)measuring an amount of nitrogen isotope in a crop sample; (b)calculating a nitrogen isotope index according to the formula (I) usingthe obtained nitrogen isotope value:δ¹⁵ N=[R sample/R reference−1]×1,000   (I) wherein δ¹⁵N is a nitrogenisotope index, R sample and R reference are ¹⁵N/(¹⁵N+¹⁴N) ratio ofsample and reference, respectively; and (c) determining whether the cropbelongs to an organic crop or a conventional crop.
 6. The methodaccording to claim 5, if the nitrogen isotope index is lower than 3%,the crop is determined to be a conventional crop, and if the nitrogenisotope index is 8% or higher, the crop is determined to be an organiccrop.
 7. A method for discriminating an organic crop from a conventionalcrop, comprising: (a) measuring an amount of nitrogen isotope in a cropsample during the cultivation period at appropriate intervals; (b)calculating a pattern of nitrogen isotope index according to the formula(I) using the obtained nitrogen isotope value:δ¹⁵ N=[R sample/R reference−1]×1,000   (I) wherein δ¹⁵N is a nitrogenisotope index, R sample and R reference are ¹⁵N/(¹⁵N+¹⁴N) ratio ofsample and reference, respectively; and (c) determining whether the cropbelongs to an organic crop or a conventional crop.
 8. The methodaccording to claim 7, (a) if the nitrogen isotope index exhibits anincreasing trend during the cultivation period with time, the crop isdetermined to be a conventional crop during the cultivation period ofwhich a chemical fertilizer had been used as a sole fertilizer in theearly growth period; (b) if the nitrogen isotope index exhibits adecreasing trend after initial increasing trend, the crop is determinedto be a conventional crop during the cultivation period of which achemical fertilizer had been used as a basal fertilizer in the earlygrowth period and as an additional fertilizer in the latter growthperiod; (c) if the nitrogen isotope index exhibits almost insignificantfluctuations or a slight decreasing trend during the cultivation periodwith time, the crop is determined to be an organic crop during thecultivation period of which an organic fertilizer had been used as asole fertilizer; and (d) if the nitrogen isotope index exhibits adecreasing trend after initial insignificant fluctuating trend duringthe cultivation period with time, the crop is determined to be aconventional crop during the cultivation period of which an organicfertilizer had been used as a basal fertilizer in the early growthperiod and a chemical fertilizer had been used as an additionalfertilizer in the latter growth period.
 9. A method for discriminatingan organic crop from a conventional crop or an organic farmland from aconventional farmland, comprising; (a) measuring an amount of nitrogenisotope in a soil sample and a crop sample from a farmland; (b)calculating a nitrogen isotope index according to the formula (I) usingeach of the nitrogen isotope value:δ¹⁵ N=[R sample/R reference−1]×1,000   (I) wherein δ¹⁵N is a nitrogenisotope index, R sample and R reference are ¹⁵N/(¹⁵N+¹⁴N) ratio ofsample and reference, respectively; and (c) comparing the resultantnitrogen isotope index values of the soil with those of the crop todetermine whether the farmland belongs to an organic farmland or aconventional farmland, or to determine whether the crop from thefarmland belongs to an organic crop or a conventional crop.
 10. Themethod according to claim 9, (a) if the nitrogen isotope index of thecrop is lower than the nitrogen isotope index of the soil, the crop isdetermined to be a conventional crop or the farmland is determined to bea conventional farmland; and (b) if the nitrogen isotope index of thecrop is higher than the nitrogen isotope index of the soil, the crop isdetermined to be an organic crop or the farmland is determined to be anorganic farmland.
 11. The method according to claim 5 , the crop is aleaf vegetables.
 12. The method according to claim 1, the crop isselected from the group consisting of a Chinese cabbage, greens forpickling, a Brassica campestris (a Chinese spinach-like greenvegetable), a cabbage, a cauliflower, a broccoli, a Brussels sprout, anonion, a Welsh onion, a garlic, a scallion, a leek, an asparagus, alettuce, a green for salad (which is called Saladana in Japan), acelery, a spinach, a crown daisy, a parsley, a trefoil (which is calledMitsuba in Japan and is useful as herb), a dropwort, an udo (which is anAralia cordata), a Japanese ginger, a Japanese butterbur and a labiate.13. A method for discriminating an organic crop from a conventional cropor an organic farmland from a conventional farmland, comprising anycombination of the methods according to claim
 1. 14. The methodaccording to claim 13, the crop is a leaf vegetables.
 15. The methodaccording to claim 14, the crop is selected from the group consisting ofa Chinese cabbage, greens for pickling, a Brassica campestris (a Chinesespinach-like green vegetable), a cabbage, a cauliflower, a broccoli, aBrussels sprout, an onion, a Welsh onion, a garlic, a scallion, a leek,an asparagus, a lettuce, a green for salad (which is called Saladana inJapan), a celery, a spinach, a crown daisy, a parsley, a trefoil (whichis called Mitsuba in Japan and is useful as herb), a dropwort, an udo(which is an Aralia cordata), a Japanese ginger, a Japanese butterburand a labiate.